what is the area of a circle in metres if the diameter is 2.48 cm?

the diameter of a syringe plunger is 2.48 cm. I need the area in meters. I keep getting different answers depending on the way i work it out. I know that A = pi r^2.

the radius would be 1.24 cm. so pi*1.24^2 = 4.8305 cm. converted to metres would be 0.04835 m

but if I convert to metres right from the beginning the equation would be

pi*0.0124^2 = 0.0004835 m

and if i start with mm at the beginning (12.4^2mm rather than 1.24^2cm) then convert the end result the answer is different again

pi*12.4^2 = 483.05 mm converted to metres is 0.48305

which answer is the right answer/ correct method when starting with cm and wanting the end result to be in metres????